Various electrochemical sensors are known which employ enzymes to sense the presence of a compound that serves as an enzyme substrate. As just one example, Nakamura U.S. Pat. No. 4,224,125 discloses an enzyme electrode system in which an enzyme, such as glucose oxidase, is used to sense glucose. A redox compound is used to accept electrons from the enzyme. For example, Nakamura discloses press molding to the electrode a mixture of glucose oxidase cross-linked by gluteraldehyde and a fluorocarbon polymer powder together with a cation exchange resin containing potassium ferricyanide. Nakamura's electrode system consists of three electrodes: an enzyme electrode, a reference electrode, and a counter electrode.
In another example, U.S. Pat. No. 4,225,410 to Pace discloses a multi-layer enzyme sensor; for example a sensor that measures levels of lactate dehydrogenase. NAD.sup.+ is generated at a fourth electrode, and the enzymatic reaction converts it to NADH which is sensed at the monitoring electrode by undisclosed means. A barrier/counter electrode and a reference electrode are used in conjunction with the monitoring electrode. However, the surface roughness of the electrodes and the difficulty in forming a well defined electrode causes the electro chemical reaction differences between strips. A means is needed to minimize this surface variation so that the strips manufactured give more repeatable results between strips and that the calibration effort is reduced.
Each of the above references is incorporated herein by reference in its entirety.